Summary
Prevent a cold or decrease its severity
Use 500 -1500 mg of Vitamin C daily during cold season, especially if experiencing stressful situations.
Treat a cold as soon as symptoms are noticed
Use zinc gluconate lozenges with at least 13.3 mg elemental zinc every 2 hours while awake for duration of cold (it should be shorter and less severe). Or, use echinacea purpurea powdered extract at 1200 mg per day for the same effects. Be sure to recommend a high-quality echinacea product.
If more than 24 hours has elapsed, you can only treat symptoms
Consider dextromethorphan for treating cough in adults. Avoid codeine products to suppress cough. Adolescents and adults can use oral or nasal decongestants to treat nasal congestion and rhinorrhea for a few days. Antihistamines and combination products with decongestants may also be useful for adults. Topcial ipratropium can be prescribed for adults and older children for nasal symptoms. Avoid the use of antibiotics.